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The low alkali resistance of basalt fiber limits its utilization in the strong alkaline environment such as cement and concrete as the reinforcing material. Adding additive in the basalt rocks is the feasible method to enhance the alkali resistance. However, it is necessary to develop the efficient additive for basalt fiber. In this work, the effect of TiO 2 on the preparation condition, alkali resistance and mechanical properties of basalt fiber was investigated. The preparation conditions were studied by DSC, XRD and high-temperature rotational viscometer. Then the corrosion behavior of TiO 2 -basalt fibers in NaOH solution was studied via SEM/EDX, FIB/SEM and FTIR. The results indicated that the viscosity of basalt melt decreased significantly with the increasing TiO 2 content from 0% to 2%, but the crystallization tendency was not changed with TiO 2 below 2%, the upper limit for TiO 2 addition. The tensile strength increased by 20–60% because Ti4+ promoted Al3+ into the network structure and intensify the polymerization by entering the network structure as network precursor in the form of [TiO 4 ]. Meanwhile, TiO 2 in the basalt fibers formed insoluble titanium hydroxide, so the weight loss of TiO 2 -basalt fibers in NaOH solution was reduced up to 50%. Through FIB/SEM/EDX, the corrosion of basalt fiber in alkali condition is controlled by ion diffusion. The outward diffusion of Fe, Mg and Ti to the surface of fiber formed the insoluble layer, so the rate of substitution reaction between the OH− and basalt fibers was slowed down, but it also leaded to the non-uniform corrosion. • Effect of TiO 2 on alkali resistance of BF was firstly investigated systematically. • TiO 2 -BFs with excellent alkali resistance were obtained. • The tensile strength of TiO 2 -BFs increases by 22–58%. • Non-uniform corrosion of BF in alkaline solution was directly observed by FIB/SEM. [ABSTRACT FROM AUTHOR]